It is because there are a lot of postmodern and modern musical elements contained by many tracks with the usual symphonic music.Williams' created many themes for main characters and motifs:the theme of Yoda,the theme of the Imperials and Darth Vader,the theme for the love of Leia and Han Solo and a theme for Cloud City.The music is extremely effective:the theme of the Imperials is dissonant,haunting, bombastic and dark at the same time,performed by dissonant strings and a powerful brass section.The theme of Cloud City begins with real colourful tunes,then is followed by the combination of the heart-breakingly beautiful love theme and the haunting elements of the Imperials' theme to illustrate the lurking of danger that is presented by the Evil Empire.Yoda' s Theme is slighty sad and relaxing at the same time,and there are some extremely colourful parts contained by it.The love theme of Hans Solo and Princess Leia is extremely beautiful and relaxing.The End Credits,subtitled as The Rebel Fleet is a wonderful amalgamation of the main themes.Well worth to purchase.